Process of oxidizing ores.



No. 885,328. PATENTED APR. 21, 1908.

B. E. BLDRED. PROCESS OF OXIDIZING ORES.

APPLIOATION FILED P318, 1906.

l'V/TVESISES; INVENTOR.

ing to a well known reaction.

V UNITED s'r ns; rA'r E are.

BYRON E. ELDRED, OF BRON'XVILLE, NEWYORK, ASSIGNOR TO COMBUSTION UTILITI ES COMPANY, OF NEW YORK, N. Y.

PROCESS OF OXIDIZ INGUREB.

Specification of Letters Patent.

PatentedApril 21, 1908.

To all whom it may concern: I Be it known that I, BYRON E. ELDRED, a g citizen of the United States, residing in Bronxville, in the county of Westchesteri and State of New York, have invented a icertain new and useful Process of Oxidizing Ores, of which the following is a'specification. i

This invention relates to processes of treating ores and consists in a method of regulated roasting of galena and similar sulfid ores by means of draft currents of diluted I air delivered through massesof such ore all as more fully hereinafter set forth, matters of novelty being particularly pointed out in the appended claims.

Galena and similar fusible sulfids are roasted with great difliculty by the processes now in use, particularly when rich ores and concentrates are treated. Oxidation of lead sulfid is a heat developin or exothermic reaction and tends to be self-accelerating in a measure, becoming violent and uncontrollable when free access of ordinary air is permitted. But as galena is readily fusible, such a violent reaction melts it superficially, rendering access of air to the interior of a lump impossible and producing uneven burning. Further, in such irregular roasting, there is a tendency for a portion of the sulfid to oxidize to sulfate which then reacts with another portion pf unchanged sulfid to produce sulfur dioxid and metallic lead accord- For these reasons, in the ordinary methods of roasting richore there must be a constant supervision of the charge b highly skilled'furnace men to preventv irregu ar roasting with the result of unchanged sulfids appearing in the roasted ore and to prevent t e formation of metallic lead in the furnace.

Regulation of the rate of burning'to prevent these detrimental results is not possible by the ordinary means and methods'used with other ores. Mechanical rabbling, as in continuously operating reverberatories, is not very feasible since the'readily fusible galena gums on rabbling tools. Hand -rabb'ling while,more practicable is heavy,

exhausting work and requires hi h skill on the part of the operator. Furt er, unless great care beexercised to revent fuslon, only the surface layers can e rabbled suc;

'cessfully. The process is very slow and the ore is apt to come out of the furnace, if

successfully roasted, in a fine pulverulent "purposes and partlcularly where the calcines are to be used in the smelting furnace Dusty materials of this character impede the blast in the furnace and are blown out of the stack, causing great losses. For this reason smelting furnaces often briquet such dusty calcines with lime. This is expensive and not very satisfactory as the bricks freguently prove'too Weak to sustain the bur' en of the furnace.

In the prior art, efforts have been made to obviate the stated inconvenience -by admixing greater or less quantities of inert materials, or diluents, such as lime, sand, etc., with the rich ores or concentrates to restrain the violence of the reaction and insure the production of orous, thoroughly roasted calcines. been converted into poor, it being considered less inconvenient to add an impurity which must afterwards be removed with some trouble and expense, rather than endeavor to-- trol which is not the case when t e ore itself is diluted, since the com osition of the draft currents can be instantly changed by the regplation of a valve or two;

apidity of combustion is a phenomenon depending as much upon the relative mass or concentration of the oxidant as upon that of by varying the composition of elther. For many purposes, as in this art, it may be said that air is, so to speak, too concentrated; it gives rise to reactions too violent and uncontrollable in their nature. On the other hand, if it be diluted, the reacting mass of the oxygen is lessened and undenthe laws of mass action or the phase rule, its reactivity lessens more than corresponds to the sheer dilution. This fact I have discovered may be very advantageously applied in the treatment of galena. It is merelynecessary to dilutethe draft current supplied tolthe mass of roasting ore with any inert gas in order to In ot er words, the IlCll ores have the substance oxidized; and it may be varied slow down the violence of the oxidation to any desired degree. As chea and conven ient for this purpose, I regard the products of combustion; preferably from a fuel burnin furnace, although the products from su fid roasting furnaces may be used; 'i. e.,

aseous mixtures containin sulfur dioxid. fioth may of course be used 111 special cases. Ordinarilyhowever, when desirin' to roast galena and similar sulfids to oxid, refer to use the products from fuel burning furnaces. Such products ordinarily consist of a mixture of carbon dioxid and nitrogen, with a little steam at times and some unburned gases or air. Prod-ucts richer in carbon dioxid may be obtained from lime and cement kilns and other furnaces treating carbonates. Steam I do not regard as an inactive diluent in the sense of the permanent gases mentioned for the reason that it has great reactive powers with sulfids, sulfites, etc. but in some embodiments. of my invention a modicum may be used together with the diluents stated in the draft current. It is especially useful in cases where an oxid as free as possible from sulfate-is required since it tends -to decomose intermediate sulfites which may be ormed. On the other hand, where it is desired to burn galena to lead sulfate, as in the production of a cheap white lead substitute,

steam is to be avoided and the diluent gas is.

preferabl .derived from sulfur burning furnaces, 'su ur dioxid having a s ecific action favoringithe production of su fates in this method of roasting.

While the draft currents described may be passed over the sulfid to be roasted or brought into contact therewith in any of the well known ways, in the present specific embodiment of my invention I prefer to pass them through a body of the ore in the manner hereinafter described. fFor this purpose, apparatus of the type shown in the accom anymg drawing can conveniently be used 2. though I do not in any way restrict myself to the use of any particular type of apparatus, my invention being susceptible of being carried out in many other forms of ap aratus.

In the apparatus shown in t 1e accompanying drawing, 1 designates the vessel in which the treatment is conducted, the same comprising, in the form shown, a vessel of the general nature of a shallow converter, mounted upon trunnions 2 so as to be capable of being tilted as hereinafter described, and

having a perforate false bottom 3, and a hood 4, the latter arranged to lift and having a telescopic or other suitable connection with a stack 5. The said converter is provided with means for supplying to it, and for assing through the material in treatment t erem, a draft current of any desired composition and temperature, such draft current being supplied by means of a blower 6 connected by a pipe 7 to one of-the trunnions 2,

bustion, steam or aqueous vapor, the prodple the offtake of furnace 10, and hence conwhich is hollow, and is connected by a passage 8 to the chamber 9 beneath the perfo-- rate false bottom 3 of the converter. Theinlet of this blower is connected to means for supplying hot and'cold air, products of comucts of the combustion of sulfur, etc. For this purpose I have shown an ordinary furnace 10, which may be of any type and may be used for any purpose, even one foreign to the present process, the only function of this furnace, so far as this process is concerned, being to supply products of carbon combustion and to heat the entering air, both of which operations it may obviously perform .while likewise performing a main function not in anywise related to the process herein described; and for the same purpose of suplying in redients of the draft current to the blower I have' shown a pipe 11 leading from the offtake of said furnace to the blower and provided with a, regulating valve 12; an air supply pipe 13 passing for a portion of its length t rough a heated region, as for exam- 9O stituting an air-heater; a pipe 14 connected to a suitable source of supply of products of sulfur combustion, not shown; a cold air inlet 15, and a source of supply of aqueous va por (steam, or water in the form of a spray or other form suitable topermit ready absorption by the draft current) 16; these several pipes being provided with suitable regulatmg valves 17, 18, 19 and 20, respectively.

By proper regulation of these valves a draft current of any desired constitution may be obtained.

Valves 17 and 19, controllin respectively the admission of hot and cold air, further constitute convenient means for regulating the temperature of thedraft currents. By provision of this plurality of sources of gases of different characters, I make it possible to regulate exactly conditions within the sulfid roasting chamber. I With admission of a draft current composed of cold air and products of combustion, the 'oxidationmay be checked while withthe same relative pro ortions of heated air and products of com ustion in a draft current it may be accelerated. 5 The admission of water to the draft current of air and products of combustion, cools it still further in cases where a cold but oxidizing draft current is desired, while. steam does not lower the temperature so 'much. The

steam or. water vapor while in no sense a diluent gas, is nevertheless frequently very convenient as aflording an additional means for completing the expulsion of oxidized sulfur as it has a specific dissociating action upon sulfites and similar salts.

Steam is a very suitable form of aqueous vapor to use; but as to supply steam generally requires the presence of a steam boiler, which is not always convenient or desirable,

, so adjusted that while oxidation and since the entering draft currents take up water readily, I may introduce the water in the form of a spray or'in any other suitable manner so that the water will be taken up by the draft current as aqueous vapor.

In using my process for the roasting of lead sulfid in this form'of a paratus, the converter may be preliminari y heated and the reaction started by placing a layer of charcoal or other fuel on the false bottom and getting it well alight by means of an air draft current, the valves being suitably adjusted for this purpose. A layer of the galenais then added and when the oxidation begins, the converter is filled to a suitable depth. As the oxidation progresses and heat develops it is restrainedby closing valve 19 or 17 somewhat and opening valve 12, thereby diluting the air draft with stack gases from the furnace. As the reaction proceeds, the proportion of diluent gas is increased until the exothermic tendency slackens when it is again decreased. The proportions are at all times during the early part of the roasting roceeds freely the temperature does not rise to a point where the alena would fuse or clinker. It is desirable or even roasting that the galena be kept porous until nearly all the oxidation is complete, thereby permitting the permeation of oxygen throughout the interior of all lumps of ore. The draft however, may be forced to a degree hitherto wholly unknown in this art for, since the oxidation nowhere becomes violent,- the oxidation may be safely permitted to take place in all parts of the mass of-ore undergoing treatment. In other words, instead of treating a superficial shell of material as in ordinary furnaces where the mass is mixed from time to time by hand labor, the porous mass may be simultaneouslyireated throughout. So, although the generation of heat is repressed and the possibility of clinkering obviated, yet forced working is practicable. When desiring to make oxid with little or no sulfate as is usually desirable, theprodnets of combustion from the reverberatory alone are used, but where sulfate is desired a modicum of products of combustion from a sulfid roasting furnace may be more advantage'ously used. As stated, the sulfur dioxid m such gases tends to restrain the dissociation of sulfites formed in the oxidation as a reliminary stage to the production of sulates and it also tends to su press decomposition of the sulfur trioxid o sulfates into suldioii d and oxygen. Therefore by the use of sulfur dioxid in the draft currents a free 0res,'the

be allowed to rise to thepoint of fusion or sintering of the ore and the material will re-' main porous. When ground for paint it will be found to possess great coverin power. Sulfate so produced is also welI ada ted for mixing with a fresh portion of una tered galena to form lead by the well known reaction.

In forming lead oxid, if it is' desired to market it as such, either in the form of litharge or red lead, the oxidation is also preferab y so conducted asto avoid fusion or sintering. Red lead may be made in the apparatus-shown by finishing the litharge formed in the described way by means of a draft current of hot air. But where the lead oxidis formed as a preliminary to production 'of lead in the smelter it is desirable to in a slightly'different manner. For t is purpose While porosity is still desirable, the

- proceeded throughout the mass of the lumps of ore. At this point the dilution of the air draft is discontinued and a sudden evolution of heat ermitted throu hout the mass, sintering t e lumps slight y and giving them mechanical stren th. By proper care in the regulation of the raft currents, it is thus possible to produce galena which while sweet roasted, is nevertheless of firm texture. With such proper care it is rarely necessary to use hot air for this finishing but it may be em loyed if desired. I

t is of course, obvious that many other sulfids, such asthose of copper, etc., may be roasted'in the manner described and I regard my invention as covering the treatment of any sulfid ore or concentrated by this process.

For poor galena where the natural heat of roceed' combustion is not great, it is often desirable to work with hot draft currents. It is obvious that m described method gives great latitude to t e operator since by changing the degree of the dilution and the temperature of the air, he can either force the heating or slacken it to any desired degree. Perfect control of the operation is given by simple manipulation of valves.

. What I regard as novel and desire to claim 1. The recess of oxidizing sulfid ores which consists in blowing throughan ign' ed mass of such ore a draft current of diluted ir, said aircontaining controlled proportions of a non-oxidizing diluent.

2. The process of oxidizing sulfid ores which consists in blowing through an ignited mass of such ore a draft current of air diluted with products of complete combustion in controlled proportions.

3. The process of oxidizing sulfid ores which consists in blowing through an ignited mass of such ore a draft current of air diluted with carbon dioxid in controlled proportions.

4. The process of oxidizing sulfid ores 'which consists in blowing through an ignited mass of such ore a draft current of air diluted with controlled proportions of products of complete combustion and a modicum of water vapor. Y

5. The process of oxidizing sulfid ores which consists in blowing through an ignited mass of such ore a draft current of air diluted.

with controlled proportions of carbon dioxid and with a modicum of water vapor.

6. The process of oxidizing galena which consists in blowing through an ignited mass of galena a draft current of diluted air.

7. The process ofoxidizing galena which consists in blowing through air ignited mass of galena a draft current of air diluted'with products of combustion.

8. The process of oxidizing galena which consists in blowing through an ignited mass of galena a draft current of air diluted with carbon dioxid.

9. The process of oxidizing galena which consists in blowing through an ignited mass of galena a draft current of air diluted with products of combustion and a modicum of water vapor.

10. The process of oxidizing galena which consists in blowing through an ignited mass of galena a draft current of air diluted with carbon dioxid and with a modicum of water vapor.

11. The process of oxidizing sulfid ores which consists in igniting a mass of sulfid ore and blowing therethrough a draft current of air diluted to a degree corresponding to the exothermic tendencies to the mass of ore.

12. The process of oxidizing galena which consists in igniting amass of galena and blowing therethrough a draft current of air diluted to a degree correspondingto the exothermic tendencies of the mass of ore.

13. The process of oxidizing sulfid ores which consists in igniting a mass of such ore, blowing therethrough "a current of diluted air until oxidation is nearly complete and then finishing with a draft current of undiluted air to sinter slightly the particles of the roasted mass.

14. The process of oxidizing galena which consists 111 igniting a mass of such ore, blow- 1ng therethrough a current of diluted air until oxidation is nearly complete and then finishing with a draft current of undiluted air to sinter slightly the particles of the roasted mass.

15. The process of oxidizing sulfid ores which consists in forcing through an ignited mass of the same a diluted air current of regulated temperature and dilution.

16. The process of oxidizing galena which consists in forcing through-an ignited mass of the same adiluted air current of regulated temperature and dilution.

17. The process of oxidizing sulfid ores which consists in forcing through an ignited mass of the same a diluted air current of regulated temperature and dilution and Varying said temperature and dilution to agree with the momentary needs of the ore under treat 

